Currently, night vision devices gather existing ambient light through the front lens. This light, which is made up of photons, goes into a photocathode tube that changes the photons to electrons. The electrons are then amplified to a much greater number through an electrical and chemical process. The electrons are then pushed against a phosphorus screen that changes the amplified electrons back into visible light that one sees through the eyepiece. The image produced is a green-hued and amplified re-creation of the scene being observed through the night vision device.
Some issues with these devices are that a high voltage power supply is needed, and there is room for improvement when it comes to light amplification capabilities. Furthermore, the need for these power supplies ensures that the device is bulky and not readily adaptable to thin films.